Polyolefins are hydrophobic and difficult to dye in that they lack dye sites to which dye molecules may become attached. One approach to color polyolefin fibers has been to add colored inorganic salts or stable organometallic pigments to polymer melts prior to fiber spinning. Nonvolatile acids or bases, or materials such as polyethylene oxides or metal salts, have been added to polymers prior to fiber formation to increase the affinity of the fiber for disperse, cationic, acid, or mordant dyes. Polyolefin fibers may be grafted chemically with appropriate monomers after fiber formation to improve dyeability. Textile Fibers, Dyes, Finishes, and Processes: A Concise Guide, Howard L. Needles, Noyes Publications, 1986, p. 191.
Efforts to impart acid dyeability to polyolefins, and particularly polypropylene, include the use of nitrogen-based polymer additives. For example, in U.S. Pat. No. 3,361,843, various incompatible, nitrogen-based polymers are added to polypropylene, given a treatment with high concentrations of acidic chemical reagents, and then dyed in an acid dye bath. According to U.S. Pat. No. 3,653,803, dyeing of the polypropylene fiber is somewhat improved by the method of U.S. Pat. No. 3,361,843, but processing of the fiber is difficult due to the incompatible polymer, the dye fastness properties not being reliably reproducible, and tinctorial strengths not being commercially sufficient. In U.S. Pat. Nos. 3,395,198 and 3,653,803, various compatible nitrogen-containing copolymers of ethylene and an aminoalkyl acrylate compound are disclosed that, when blended with polyolefins, render fibers formed from the blend acid dyeable. In U.S. Pat. No. 5,017,658, a fiber finishing agent is used in melt spinning dyeable polypropylene fibers obtained by blending a copolymer of an ethylene aminoalkyl acrylate with polypropylene.
In U.S. Pat. No. 4,557,958, a blend of 70% by weight polypropylene homopolymer and 30% by weight ethylene-methylacrylate copolymer is applied to a fabric of woven polyolefin as a coating stripe to prevent fraying of the fabric when the fabric is cut. In U.S. Pat. No. 4,853,290, a blend of ethylene-acrylic acid copolymer and ethylene-methylacrylate copolymer is coextruded onto a polypropylene film to serve as an adhesive or tie layer to a second polymer.
In U.S. Pat. No. 4,782,110, melt processible multiphase thermoplastic compositions are described that can be formed into various shapes by compression molding, injection molding, blow molding, and extrusion. The composition comprises a blend of crystalline polyolefin resin forming the continuous phase of the composition and a cross-linked elastomer of an ethylene alkyl acrylate copolymer forming the discontinuous phase of a composition. The elastomer consists of units derived from ethylene, an alkyl ester of acrylic acid wherein the alkyl group contains 1 to 6 carbon atoms, and a monoalkyl ester of 1,4-butenedioic acid wherein the alkyl group contains 1 to 6 carbon atoms.
U.S. Pat. Nos. 3,373,222 and 3,373,223 disclose polymeric blends comprising polyolefin resin, polyamide resin, and either a carboxylated polyethylene, an ethylene-acrylic, or a methacrylic acid copolymer. Homogeneous polymeric blends have utility in the preparation of films useful in the packaging industry and in the preparation of plastic bottles and other containers that require a high degree of impermeability.
U.S. Pat. No. 3,454,215 discloses a dyeable polypropylene composition comprising a polyamide and ethylene copolymer. The composition may consist of a uniform admixture of polypropylene, a low molecular weight thermoplastic unreactive polyamide, and an additional polymer selected from a group consisting of copolymers of ethylene and an ethylenically unsaturated ester of a saturated fatty acid or a hydrolyzed product of such copolymers. U.K. Patent Specification No. 998,439 also discloses a thermoplastic composition comprising polyamides and olefin copolymers.
U.S. Pat. No. 5,017,658 discloses a dyeable polypropylene composition including a copolymer of an aminoalkyl acrylate with polypropylene. U.S. Pat. No. 4,368,295 discloses a film produced by a melt extrusion process made from compositions containing an olefin polymer, a linear polyester, and a carboxylated polyolefin. U.S. Pat. No. 4, 174,743 discloses split-fiber, thread, and film products comprising polypropylene and one or more polyesters and/or polyamides.
A chapter entitled "Dyeing of Polypropylene Fibers" in Polypropylene Fibers, Science and Technology by Mike Ahmed provides a comprehensive study of the technology involved in dyeing polypropylene fibers in the mid 1950s to the 1980s. Section IV. 1 regarding mordant-dyeable fibers discusses problems relating to light fastness, wash fastness, and crock fastness of certain dyes. The study concludes that the fastness properties of disperse-dyeable polypropylene fibers are generally unacceptable to the textile trade.
An article entitled "Surface Dyeable Modified PP BCF Yarns" in Chemiefasern/Textilindustrie, Vol. 41/93, October 1991 discusses adding a modifier to PP BCF yarn. A brochure entitled Polymer Compounding by Eastman Chemical Products, Inc. discusses Epolene E-43 wax as a compatibilizer for nylon/polypropylene composites. An articles entitled "Morphological and Mechanical Properties of Extruded Polypropylene/Nylon-6 Blends" by Wan Gheluwe et al. discusses nylon and polypropylene blends using Zytel 211 as a compatibilizer. An article entitled "New Functional Materials for Absorbent Products" by Dr. Suzuki in The New Nonwoven World, Fall 1993 discusses new polypropylene materials for absorbent products.
In an article entitled "Polymer Morphology on the Dyeing Properties of Synthetic Fibers," Keith Silkstone reviews some of the prior art efforts conducted with regard to proposing morphological changes in the fiber production for marginal dye uptakes in polypropylene. Other relevant articles are "Dyeing Synthetic Fibers," H.E. Schroeder, C&EN, Sep. 10, 1956; "Dyes for Hydrophobic Fibers," H.E. Schroeder et at., Textile Research Journal, Vol. 28, April 1957; and "The Influence of Polymer Morphology on the Dyeing Properties of Synthetic Fibers," Keith Silkstone, Rev. Prog. Coloration, Vol. 12, 1982.
The need exists for improved polyolefin compositions and materials that will be commercially dyeable with a broad range of dyes. A particular need exists for polypropylene-based compositions that can be used to manufacture fibers that are spinnable and may be formed into fabric sheets including nonwoven fibers.